Seen: ICOP member Mr. Jim Stamm said:
Location = Tucson, Arizona (USA)
Longitude = 110.9645 W
Latitude = 32.4204 N
Elevation = 842 meters
Time Zone = -7.0 hours
Surface conditions at 14:00 Local Time
Temperature = 90 degrees Celsius
Relative Humidity = 9 percent
Topocentric and local time values from “Accurate Times”:
Sunset (at sea level) = 18:02
Moonset (at sea level) = 18:07
Time from new moon at 18:04 = 19 hr. 41 min.
Moon lag time = 5 minutes
Relative Altitude = 1.14 degrees
Elongation from sun = 9.80 degrees
Crescent width = 13 arcseconds
Illumination = 0.73 percent
Crescent first observed through 8” SC telescope:
Time = 14:40
Altitude = 34.2 degrees
Crescent steadily observed through 8” SC telescope:
Time = 16:50
Altitude = 12.9 degrees
I began observing at 13:00 local time, under ideal conditions. There were the usual teasers, and some were convincing enough to keep me at the eyepiece. At 14:40 I saw what looked like a short arc, and when I centered the image, it was still there! However, the image would never stay for more than a few seconds, and at one point when I “positively” knew where it was, it wasn’t there. So I ran through the procedure again, and when the time came (16:50), a ten degree image of the crescent was in the center of the eyepiece. It remained steady. I left the telescope to get this report out.
When I returned to my scope after submitting the first part of the report, the image was still in the field of view. After a few minutes, it began to fade, and once it was gone, I was never able to acquire it again. I would estimate that time to be about 1710 (Local). I followed the empty field all the way until Moonset.
The most interesting aspect of the observation was the expected contrast. The atmosphere was exceptionally clear, and I had a deep blue field in my 50x eyepiece at less than 10 degrees from the sun. I used Venus, Saturn, Jupiter, and Regulus to set the focus on the scope and tweak the setting circles. I then ran through several off- setting sequences with the sun to acquire the precise field of the Moon's crescent. The first couple of runs produced nothing but the "teasers" mentioned in the first part of this report. I don't think any of them were images of the crescent. These observations were when the Moon had an altitude of 35-43 degrees. Only after the Moon had dropped to an altitude of about 34 degrees did I get images that looked like genuine crescent images. This is AFTER the sky color had "degraded" from a deep blue to a silvery blue. During the deep blue phase I had the feeling that the sky was blue, but the "noise" from my retina was more like the gray that I expected the crescent to be. The acquisition of the first images was when the whole field was like the "noise". I had lost the expected contrast with the blue sky that I had aimed for by beginning the observations at 1300. Then after the Moon had dropped to about 13 degrees, I acquired a steady stable image of the crescent. The blue background was gone by then.
Although this is what I had observed during previous observations, it was contrary to what I expected. The sky was still superb, but I thought that the color of the reflected sunlight against the bluest of background skies would give me the best chance of seeing the short crescent. This is not what happened.
What did happen? Are the colors deceiving my expectations of contrast? Is there a filter quality of the atmosphere that may be enhancing the contrast at a lower altitude? Is there some kind of relationship between scattered sunlight and the reflected light of the crescent? Help!!
Observer(s): Jim Stamm
Note from ICOP: Kindly highly notice that the observer was able to see the crescent before sunset using 8" telescope, but he was NOT able to see the crescent after sunset even by telescope.